The present invention relates to a semiconductor device using a silicon nitride film as an insulating film, and a method of manufacturing the same.
A semiconductor memory device has been widely used as a memory device for use in an information processing apparatus in recent years. The semiconductor memory device is highly resistive to mechanical shock due to the absence of a mechanical driving mechanism. In addition, it is possible for the semiconductor memory to gain high-speed access since a reading-out operation is electrically performed.
However, the tendency toward miniaturization of memory cells, that is, high integration of the semiconductor memory device, has been accelerated by recent progress in semiconductor technologies, particularly in miniaturization technologies. With the high integration of the semiconductor memory device, problems are raised regarding memory cell storage characteristics.
For example, in a DRAM having a memory cell consisting of a MOS transistor and a capacitor connected in series, capacitance is inclined to decrease with reduction in capacitor area due to the high integration. As a result, problems called "soft error" occur. The soft errors are phenomena where a different memory is mistakenly read out, and where a stored memory data is broken by an .alpha. ray.
To solve the soft error problems, it is important that the capacitance is maintained even if the memory cell is reduced in size. To attain this, it is necessary to increase a capacitor area as well as to reduce thickness of a capacitor insulating film.
As the capacitor insulating film, a silicon nitride film, which has a higher dielectric constant than a silicon oxide film, has been widely used. The silicon nitride film of this type has hitherto been formed by a low pressure CVD method. However, the silicon nitride film thus formed has a drawback in that a leakage current is likely to increase.